﻿/*
	Copyright (C) 2011-2012 Bernardo van der Wal <bernardo@thebigb.nl>

	Permission is hereby granted, free of charge, to any person obtaining a copy of
	this software and associated documentation files (the "Software"), to deal in
	the Software without restriction, including without limitation the rights to
	use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
	of the Software, and to permit persons to whom the Software is furnished to do
	so, subject to the following conditions:

	The above copyright notice and this permission notice shall be included in all
	copies or substantial portions of the Software.

	THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
	AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
	SOFTWARE.
*/
using System;

namespace TheBigB.JsonSerializerLite.BuiltinExtensions
{
	/// 
	/// DateTime serializer extension.
	/// 
	/// This extension takes a DateTime object and converts it to a Javascript
	/// Date object compatible time notation (Unix/POSIX time).
	/// 
	/// Changelog:
	///		2012-09-16
	///			- Extension created
	///

	/// <summary>
	/// JSON serializer extension that allows serialization and deserialization
	/// for the DateTime type.
	/// </summary>
	class DateTimeSerializer : IJsonSerializerExtension
	{
		/// <summary>
		/// Holds the start of the Unix epoch in DateTime ticks
		/// </summary>
		private static readonly long UnixEpochTicks = new DateTime(1970, 1, 1).Ticks;

		public Type GetTargetType()
		{
			return typeof(DateTime);
		}

		public string Serialize(object input, JsonSerializer serializerInstance)
		{
			return this.SerializeDateTime((DateTime)input).ToString();
		}

		public object Deserialize(string input, Type targetType, JsonSerializer serializerInstance)
		{
			try
			{
				long timestamp = Int64.Parse(input);
				return this.DeserializeDateTime(timestamp);
			}
			catch (Exception)
			{
				return DateTime.MinValue;
			}
		}

		/// <summary>
		/// Takes the provided DateTime object and returns the number of seconds
		/// in Unix/POSIX time, compatible with the Javascript Date object.
		/// </summary>
		/// <param name="timestamp">Timestamp object to serialize</param>
		/// <returns>Timestamp in Unix/POSIX time</returns>
		private long SerializeDateTime(DateTime timestamp)
		{
			return (long)((timestamp.ToUniversalTime().Ticks - UnixEpochTicks) / 10000);
		}

		/// <summary>
		/// Converts time represented in Unix/POSIX time to a C# native DateTime
		/// object.
		/// </summary>
		/// <param name="timestamp">Unix/POSIX timestamp</param>
		/// <returns>C# DateTime object</returns>
		private DateTime DeserializeDateTime(long timestamp)
		{
			return new DateTime(1970, 1, 1).AddMilliseconds(timestamp).ToLocalTime();
		}
	}
}
